Parasites are known to subtract resources from their hosts to such an extent that they compromise their fitness. The evolution of the parasite-host interaction has generated a constant race, in which the host seeks ways to get rid of the parasites or to reduce the damage, and the parasites seek to improve the use of resources provided by the host. This pressure imposed by the interaction leads to adaptations such as strange or different behavior in infected hosts. Parasites with a heteroxenous life cycle require two or more hosts to complete their life cycle, namely a gastropod mollusk, a fish and the definitive host, a piscivorous bird. They encyst their larvae in the muscles, eyes or brain of fish and require a piscivorous bird to eat their host, passing trophically to the definitive host and thus completing their life cycle. The purpose of this study proposal is to understand the strategies of parasite manipulation on their hosts. To this end, laboratory experiments will be carried out where we will control some variables to observe the behavioral differences in fish with high parasitic intensities. We expect to find encysted parasites in the muscles and brain of the cichlid Aequidens epae Kullander, 1995 with altered behavior. The hypothesis that fish with high parasitic intensities tend to migrate to the surface of the water swimming sideways and writhing will be tested.